Freight containers and the more relevant common offshore equipment containers discussed herein are subject to international convention rules governing their construction and periodic safety inspection. Such offshore containers are generally rectangular and vary in length from ten to over forty feet and are constructed of heavy steel tubular members with expanded metal plating. The containers are also equipped with their own cable slings. These containers and their lifting slings must be examined and certified when new and re-inspected every 6 months and pass a proof load test of up to two and one-half times their safe working load under various conditions every 24 months. With safe working loads of these containers reaching 24 tons or more, the testing apparatus is often quite large and heavy itself. Therefore, most testing is conducted at onshore facilities. This requires that the containers be transported great distances to these facilities at significant expense plus taking the containers out of service for long periods of time, incurring even greater expense.
Recently methods have been devised for carrying out the required load test on location such as the offshore rig itself or near the vicinity to the supply point utilizing the containers. Such methods include water bag weights. This allows for easy storage but requires a great deal of time to set up and fill the bags. Movement of the offshore rig produces an unstable platform and thus tends to overload some areas of the container more than others, producing an imprecise test. Further, such testing requires that the container be lifted off the deck with the water bags in place producing a potentially unsafe situation if the load shifts for any reason.